Adventure Time: Fionna and Cake is an American adult animated television series developed by Adam Muto and serves as a spin-off to the Cartoon Network series Adventure Time. The third-released series in the franchise, it premiered via the streaming service Max on August 31, 2023. In December of the same year, Max announced that the show had been renewed for a second season.

The series focuses on the eponymous Fionna and Cake the Cat, alternate-universe versions of Adventure Time's main characters: Finn the Human and Jake the Dog. Also featured is Simon Petrikov, who originally appeared in Adventure Time as the Ice King. Fred Seibert and Sam Register executive produce, along with Muto, who had served as showrunner for the latter half of Adventure Time and oversaw production of the Distant Lands specials.